In this video, we're going to distinguish between essential and non-essential amino acids. It turns out that biochemists use the word "essential" in a slightly different way than our everyday use of the word essential. Normally, in our everyday use, essential means absolutely required. However, if you apply that to amino acids, then all of the amino acids are really essential because they're all absolutely required. If you're missing one of the amino acids, then it's likely that you're missing a component of one of your proteins, and that won't be a good thing. All of the amino acids are essential and needed for survival. So, that's not what biochemists mean by essential. When biochemists say essential amino acids, what they actually mean is that these amino acids cannot be generated by the organism itself. They cannot be synthesized by the organism. The only way the organism can obtain these amino acids is through consumption in their diet. And that's all "essential" means: essential amino acids are amino acids that must be consumed in the diet because the organism cannot generate those amino acids. Non-essential amino acids can actually be generated by the organism. They can be synthesized. It's not necessary for the organism to directly consume these amino acids because they can consume other things and then synthesize the non-essential amino acids.
In our example below, we've got a list of all the essential and non-essential amino acids for humans and mammals. There are actually 9 essential amino acids and all the others fall under non-essential. Also note that there's a little star next to arginine, which is listed under non-essential, and that's because arginine is kind of on the fence here. Sometimes it's listed as essential, other times as non-essential. It's because humans and mammals can synthesize arginine, but a lot of the arginine is broken down into urea and is not available to be put into proteins. So, sometimes, arginine needs to be consumed by animals, by mammals, and by humans. That's why it's kind of on the fence here. It's good to note that your professor might list it as essential.
On both sides of the chart are two different mnemonics to help you memorize those essential amino acids, as it's likely that your professor will want you to know which amino acids are essential and must be consumed in our diet. The one on the left is a mnemonic I found online that seems to help a lot of different people. It’s "try this VIP mol." "Tryptophan" for "try," "Threonine" for "this," "Histidine" for "his," "Valine" for "VIP V," "Isoleucine" for "I," and "Phenylalanine" for "P" (note: the "P" is not for "Proline" as Proline is not essential). The "MOL" part: "Methionine" for "M," "Alanine" is ignored as it is non-essential, and the two "L’s" are for the two amino acids with "L’s" in them. The one on the right is one I created. "I let Martin Luther King trip his favorite video character." In this mnemonic, "Isoleucine" for "I let," "Threonine" for "Let," "Methionine, Leucine, Lysine" for "MLK," "Tryptophan" for "Trip," "Phenylalanine" for "Favorite," and "Valine" for "Video." This mnemonic visualizes a scenario where Martin Luther King trip his favorite video character, Charlie Brown, who then asks, "Was that essential?" In the dream, Martin Luther King responds, "Yes, that was essential."
If you like any of these mnemonics, go ahead and use them. What we’ll do now is apply this knowledge and these mnemonics in our practice problems. I’ll see you guys in those videos.
